Contact lenses are medical devices that must be handled properly to avoid eye injuries. Always wash, rinse and dry your hands before handling a lens.

Each lens surface can be curved, flat (plano) or both (bi-convex and plano-concave). Each of these curved surfaces can be a section of a sphere, aspheric or cylindrical.

What is a contact lens?

Contact lenses sit on top of the cornea (the clear front part of your eye) and help make your vision clearer, just like eyeglasses do. There are a variety of contact lens types, including decorative lenses that change the color or appearance of your eyes and specialty contacts to treat medical conditions.

Most contact lenses today are made of plastics called hydrogels that incorporate water for added hydration. Some of the most advanced contact lenses are silicone hydrogels, which allow even more oxygen to reach your eye. They can be worn as "daily wear" (DW) or extended wear ("EW") lenses.

Other kinds of contact lenses include rigid gas permeable (RGP) and hybrid lenses. RGP lenses are more durable than soft lenses and can correct astigmatism better, but they can be less comfortable. Hybrid lenses combine the durability of RGP with the comfort of soft contacts. They are usually inserted once a day, but can also be worn overnight.

How does a contact lens work?

Contact lenses correct vision by manipulating light so it focuses on the retina (the light-sensitive structure at the back of the eye). When light comes into focus before the retina, you are nearsighted; when it focuses behind the retina, you are farsighted. Contact lenses come in many forms to help with a range of vision issues, including astigmatism.

The most common types of contact lenses are soft and made of a material called polymer. Some brands are now making a type of contact lens that contains silicone hydrogel, which allows more oxygen to pass through the lens and dehydrates less.

Rigid gas permeable (RGP) lenses are a harder type of lens. They have a rigid zone that extends over the sclera, or white part of the eye. They are less prone to collecting irritating deposits but require a more precise fit than soft contact lenses and may take some getting used to at first. RGP lenses are also available in bifocals and multifocals.

How do I put a contact lens in my eye?

First, wash your hands. Be sure to use plain soap without extra moisturizers or perfumes as this prevents you from introducing germs to your eyes.

Then open your satchet of contact lenses and take a lens out and place it on the tip of your index finger (or the hand you plan to use to insert the contact into your eye). Look closely at the lens, if it looks like a bowl or a sphere cut in half that is correct. If it is inside out or has flaring edges, then gently flip the lens to correct it.

Next, wet the lens with a squirt of contact solution. This helps the lens stick to your finger and it also keeps your hand moist as you move forward with putting it in your eye. Some people prefer to close their eye and use the other hand to “look” into the mirror as they put in the lens, but it is up to you how you want to do it.

How do I remove a contact lens?

If you're wearing rigid gas permeable (RGP) contact lenses and one gets stuck in your eye, it's best to get the lens out before it causes any damage. Luckily, it's relatively easy to remove the lens.

Start by washing your hands, then using saline or rewetting drops in your eyes to lubricate and loosen the lens. Gently close your eye and massage the area, trying to encourage the lens to move to a position where it's easier to retrieve.

Next, use the middle finger of your nondominant hand to pull up on your upper eyelid and the middle finger of your dominant hand to pull down on your lower eyelid. With your index and thumb, position your fingers in a "V" shape over the lens to create some gripping force. Then, slowly slide the lens down onto the white part of your eye to break the suction. Afterward, you should be able to easily pinch out the lens.